Engelmann Proceedings of the American Academy of Arts and Sciences 3: 297, 1856

Herbarium (possible); Herbarium (later changed to O. macrorhiza); Herbarium (as O. nemorlis/O. macateei); Drawing (United States Pacific Railroad and Other Reports [USPRR], plate XI/archival material);

Original Description

What is Opuntia fusco-atra?

O. fusco-atra (sometimes fuscoatra) is a little-known and poorly documented prickly pear. It is reported to grow west of Houston, Texas on sterile prairies. 

Details

This Opuntia is purported to have stout brown, almost black, spines on small prostrate pads. The pads are orbicular or obovate. The unusually stout spines on small pads are reported to give the plant a distinct appearance. The cladodes are 5-7 cm long and the spines are 2-2.5 cm long. A lower, less stout, spine may be present. The drawing shows one major spine per areole. The flowers are about 4.5 inches in diameter, the petals are very broad, and the ovary is about 2.5 cm long.  

 

Ploidy is unknown. 

Other Notes

Some botanists consider that O. nemoralis is a synonym of O. fusco-atra, or even O. macrorhiza. From the drawing, it appears, that these may not by synonymous. It should be noted that the drawing shows many black spines, were as the black and white photos from the Griffiths’ Glass Negatives Web Page, show fewer spines. 

The authors have not observed it.